In the field of housing or of building in general, radio transmission is being used increasingly frequently in order to remotely control elements electrically powered by the line supply (typically 230 V AC 50 Hz or 120 V AC 60 Hz), or the mains.
The applicant is marketing, under the reference SLT and IPSO, a motor for driving blinds or roller shutters, with radio remote control. This motor is of tubular shape and is placed inside a winding tube made of steel, on which the product to be wound is placed. Under these conditions, the radio integrated with the motor has an antenna in the form of a semirigid wire cord, coming out of the tubular motor and also coming out of the winding tube over a suitable distance, for example λ/4 (a quarter wavelength), that is 17 cm for a frequency of 433 MHz or about 8 cm for a frequency of 868 MHz.
This type of antenna has the drawback of being fragile, relative to the weight of the motor, which entails particular precautions with handling and packaging. Furthermore, the housing for the winding tube of the blind or roller shutter often consists of a steel, or even an aluminium, casing. In this unfavourable environment, the range of the antenna may be considerably reduced. Furthermore, if the device is externally mounted on a reinforced concrete wall this reduction is more pronounced.
It should be noted that various solutions have been proposed to make it easy to integrate a radio receiver with such a motor. Thus EP-0-921 266-A2 discloses direct placement of the radio receiver inside the motor tube. No explicit mention is made of the arrangement of the antenna. In the product marketed by TOPELECTRO International, in Spain, under the reference TOPELECTRO JUNIOR, the quarter-wave antenna is arranged completely independently of the line cord or mains lead, partially wound over itself so as to take up less space. This arrangement describes an extremely limited range.
In patent FR-2 743 390, the radio receiver is placed in a control box independently of the motor tube, but with easy integration with the roller shutter casing or with a blind fastening. No mention is made whatsoever of a particular arrangement for the antenna within this box.
In separate applications, it has also been proposed to use the power supply cable from the mains as mechanical support for an antenna. Examples of radio-controlled devices having an antenna lying along the mains power supply cable, but without mains coupling, are proposed in U.S. Pat. No. 2,218,830, GB-A-340 389, U.S. Pat. No. 6,104,920, U.S. Pat. No. 5,351,284 or else U.S. Pat. No. 3,863,157. U.S. Pat. No. 2,218,830 provides an antenna for a radio or television receiver, having an antenna formed by a wire associated with the power supply cable. The antenna is associated with this cable so as to minimize the coupling between the antenna and the line cord or mains lead. The benefit is then to have a nondirectional antenna of a length properly calibrated by the manufacturer. Thus, adjustment of the HF circuit does not depend on variable parameters, as is the case with an external antenna left to the initiative of the installer. GB-A-340 389 proposes, for such receivers, directly using a portion of the mains cable, isolated upstream and downstream by two terminator circuits, as an antenna. At the frequency of the signal, everything takes place as if the cable was a single wire acting as an aerial cord. Both terminators provide isolation between the signals received by the cable acting as an antenna and the mains signals. FIG. 4 of U.S. Pat. No. 6,104,920 provides a device of the same type as this British patent. GB-A-702 525 provides a solution of the same type for television receivers. The signal received over the part of the power supply conductors forming an antenna is coupled in the receiver by means of a coupling coil and a coaxial cable.
U.S. Pat. No. 5,351,284 concerns the base unit of a wireless telephone. The telescopic antenna is replaced by a wire coupled either to the telephone line, or to the mains lead, and; it is expressly stated that the telephone line or the mains lead does not contribute to the antenna reception. U.S. Pat. No. 3,863,157 provides a device of the same type, in which the connection wires between the amplifier of a stereo receiver and the loudspeakers are also used as antenna wires. Provision; is again made for separation of both functions. In all these documents, the objective sought is to replace a fragile or unsightly aerial with a portion of a cable which is used for other purposes. Consequently, these documents specify that it is important to isolate the signals received on the cable acting as an aerial from the signals transmitted on the cable in normal use.
U.S. Pat. No. 4,032,723 shows a cordless duplex telephone system where one of the elements of a doublet antenna consists of a conductor from the mains cable. The teaching of this document is similar to that of the previous documents—the antenna however being of another type.
Moreover, it has been proposed to use the mains as a receiving antenna. BUBENDORFF markets, under the reference “id”, a motor for roller shutters with an integral radio not having a specific antenna, for which the mains is generally used as a receiving antenna, and using an electrical connection via a capacitor between the inlet terminal of a line cord or mains lead and the RF input point of the receiving circuit. It should be noted that such an arrangement makes the electronic card particularly sensitive to disruption from high-energy interference conveyed by the mains.
For other fields of the prior art, similar teaching appears in documents U.S. Pat. No. 2,581,983, U.S. Pat. No. 3,290,601, U.S. Pat. No. 2,915,627 or else U.S. Pat. No. 4,507,646. U.S. Pat. No. 2,581,983 discloses coupling a radiofrequency receiving circuit with the mains power supply cable of a radio receiver. The coupling point is separated by a quarter or an eighth wavelength from the receiver frame, which is connected to earth. U.S. Pat. No. 3,290,601 is an improvement to this patent, and proposes simply to form a doublet antenna by associating a single pole antenna with the previous device. U.S. Pat. No. 2,915,627 provides an antenna for a radio receiver. A cylindrical conductor having a length between a quarter and half wavelength of the radiofrequency signals surrounds the power supply cable. The cylindrical conductor allows the radiofrequency signals received by the mains, which acts as an antenna, to transmit to a radiofrequency receiver. U.S. Pat. No. 4,507,646 discloses using the wires of the mains as antenna for the transmitter or the receiver for a paging system. The; the nature of the circuit coupling the radiofrequency receiver or transmitter to the mains is not specified.
The devices described in these various documents have the objective of avoiding the use of a dedicated antenna, by using the mains conductors as an antenna.
This solution involves accurately controlling the point coupling the radiofrequency receiver or transmitter to the mains conductors. Without; such control of the coupling point, this solution in fact has serious drawbacks in terms of selectivity and of susceptibility to broadband high-energy interference conveyed by the mains. Furthermore, the galvanic isolation may entail the use of particularly well-protected capacitors.
In the special case of tubular motors, the invention provides a solution which makes it possible to control a motor by radio, with good reliability. The solution is applicable to all the use environments for these motors, and it is simple to implement.